Acetohydrazide → 3-methyl-6,7-dihydro-5H-pyrrolo[2,1-c][1,2,4]triazole-7-carboxylic acid

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Reaction Steps

Dissolved commercially available ethyl 2-oxopyrrolidine-3-carboxylate (2.50 g, 15.91 mmol) in 30 mL dichloromethane in 50 mL round bottom flask. To this solution was added trimethyloxonium tetrafluoroborate (2.59 g, 17.5 mmol) as a solid and rinsed with 20 mL dichloromethane. The resulting mixture was stirred at room temperature for two h and LC/MS indicated that the intermediate methyl 5-methoxy-3,4-dihydro-2H-pyrrole-4-carboxylate had formed. At this point, acetohydrazide (1.18 g, 15.91 mmol) was introduced as a solid to the mixture and the resulting solution was stirred at room temperature for 3 h. The solution was then concentrated under vacuum to remove all dichloromethane and the residue was then taken up in 100 mL n-butanol which was heated to reflux in an oil bath set at 120° C. overnight. The solution was cooled to room temperature and concentrated under vacuum. The residue was purified via sixteen 1500 μm silica gel preparative plates eluting with 90:10 dichloromethane:methanol solvent system. The product was extracted from the silica gel using 85:15 dichloromethane:methanol which afforded the title compound (454 mg, 11%). 1H NMR (500 MHz DMSO-d6) δ: 4.16-4.06 (m, 1H), 4.00-3.88 (m, 1H), 2.85-2.78 (m, 1H), 2.29 (s, 3H), 1.55 (dt, J=6.7, 13.9 Hz, 2H), 1.32 (dt, J=6.7, 14.0 Hz, 2H), 0.88 (t, J=7.5 Hz, 3H). LC-MS: m/z (ES)=196 (MH)+.

Provenance & Evidence